Process of making hydrosulfites.



IPatented. June 6, 1905.

PATENT OFFICE.

LOUIS DESCAMPS, OF LILLE, FRANCE.

PROCESS OF' MAKING l-IYDROSULFITES.

SPECIFICATION forming part of Letters Patent No. 791,67 5, dated June 6,1905.

Application filed. July 6, 1903. Serial No. 164,444.

T on whom it may concern:

Be it known that I, LoUIs DESOAMPS, a citizen of the French Republic,and a resident of Lille, N 0rd, France, have invented certain new anduseful Improvements in Processes of Making Hydrosullites, of which thefollowing is a full, clear, and exact specification.

'My invention relates to improvements in the process of makinghydrosulfites and to the product obtained therefrom.

The object of my invention is to provide a process by which thehydrosulfites may be economically produced on a commercial scale and bymeans of which may be produced a stable hydrosulfit ethat is to say, ahydrosulfite which may be kept under ordinary conditions for aconsiderable length of time without decomposition.

My improved process consists in the quick addition of areducing-powdersuch as zinc, iron, tin, or the likein a very fine andpure condition and in quantity slightly in excess of that theoreticallyrequired to a concentrated solution of sulfurous acid of industrialpuritythat is, as free as possible from other acids and impurities. Thesolution may be an aqueous, alcoholic, glycerinous, or other solution ofsulfurous acid. The mixture is stirred quickly, then allowed to deposit,and

the solution finally decanted. It is of great importance that the wholeof the sulfurous acid be transformed into hydrosulfite, and

therefore the reducing-powder, such as zinc,

must be in slight excess, as heretofore stated,

' for if even a single molecule of the acid should remain free adecomposition will take place. By thus instantaneously adding the wholequantity of the reducing-powder to the sulfurous acid the temperature ofthe liquid mass suddenly rises. I do not attempt to prevent by coolingthis rising,which, if not excessive, is essential for instantaneouslyand completely succeeding with the reaction. This rapid action at anelevated temperature is of great importance, for the product is easilydecomposed if the whole of the acid is not transformed. After havingbrought the reaction to an end 1 allow the slight undissolved excess ofthe reducingpowder and the impurities that 5 might be present in spiteof all precautions to deposit and decant the liquid. The zinchydrosulfite thus obtained is ready to be used in reducing indigo or forother purposes, or the solution can be transformed into otherhydrosulfites by addition of either bases, like lime, sodium hydrate,baryta, &c., or salts acting by double decomposition, such as acetate ofcalcium or of barium or the like.

The products obtained by my process are entirely stable and differ bythis quality advantageously from the hydrosulfites prepared according toother processes. The economy of. the reaction is sufficient, and theyield is almost theoretical. The degree of reduction of my hydrosulfitescompared with those prepared according to other processes is very high.There are also no difficulties in obtaining by my process a pastyhydrosulfite of calcium, one and three-tenths (1.3) parts of which aresufficient to reduce one (1) part of pure indigo.

In practically carrying out my process I proceed, for instance,according to the following axample: Six hundred, and seventy (670) gramsof very pure zinc-dust are added at oncethat is to say, at one chargetoone (1) kilogram of sulfurous acid in the form of an aqueous solution.The whole is quickly and intimately mixed and the solution decanted. Thereaction takes place according to the following equation:

From the zinc-hydrosulfite solution thus obtained calcium hydrosulfiteis readily obtained by adding to the said solution caustic lime orsubjecting it to double decomposition by adding a salt of lime, such asthe acetate of lime. This reaction proceeds in a manner well understoodby chemists and results in a pure precipitate of the hydrosulfite ofcalcium, whose formula is CaszOi. It precipitates in a pasty form, oneand three-tenths of the same being sufiicient to reduce one part of pureindigo.

The hydrosulfites produced by the process described and which have thegeneral formula M8204 (where Mdenotesa bivalent metal) are especiallyapplicable for the reduction of indigo, sulfur dyes, and othersubstances for decolorizing paper-pulp or sugar-juices, for thepurification of water for antiseptic purposes, and the like.

Having thus fully described my invention, What I claim is 1. The processof producing hydrosulfites of metals, which consists in quickly adding,in one charge, a reducing-powder of finely-divided metal slightly inexcess of the theoretical amount, to a solution of sulfurous acid, andallowing the reaction to proceed without regulation of the temperature.

2. The process of producing hydrosulfites of metals which consists inquickly adding, in one charge, a reducing-powder of finely-divided metalslightly in excess of the theoret-. wical amount, to a solution ofsulfurous acid,

then quickly stirring the mixture, allowing the reaction to proceedwithout regulation of mixture, allowing the reaction to proceed withoutregulation of the temperature, and, finally, decanting the solution.

4. The process which consists in quickly adding pure zinc in afinely-divided condition, at one charge and slightly in excess, to aconcentrated solution of sulfurous acid, stirring the mixture andallowing the reaction to proceed without regulation of the temperature,then separating the solution and then adding a calcium compound to saidsolution.

5. The process which consists in quickly adding pure zinc in afinely-divided condition, at one charge and slightly in excess, to aconcentrated solution of sulfurous acid, stirring the mixture andallowing the reaction to proceed without regulation of the temperature,then separating the solution and then adding caustic lime to saidsolution.

In testimony that I claim the foregoing as my invention I have signed myname in presence of two subscribing witnesses.

LOUIS DESGAMPS.

Witnesses:

JOSEPH HARDING, HY GARVILLE.

